Around 12:08 p.m. on Saturday, November 10, eastern Kentucky was hit by a small earthquake registering 4.3 on the Richter scale. The quake was felt as far afield as Cincinnati and Atlanta, where residents were shaken by the relatively uncommon event. Thankfully, the strength of the earthquake was minor, as was the damage sustained in areas near the epicenter, and no individuals appear to have been hurt.
The temblor was caused by slippage at moderate depth (19.9 km below the surface) in the vicinity of Whitesburg, in a relatively stable part of the North American tectonic plate. As many may remember from their middle school science classes, earthquakes result from the sudden movement of one part of the Earth’s crust relative to another, with most earthquakes occurring at the boundaries of large slabs of the Earth’s crust, known as tectonic plates. What makes quakes in places like Whitesburg so interesting is that can occur hundreds, even thousands of miles from the nearest tectonic plate boundary. In fact, one of the strongest quakes to ever afflict the United States, the New Madrid seismic event of 1812, occurred by the Arkansas-Missouri border, nowhere near the edges of the North American plate.
Throughout the entire continent, the bedrock is fractured from hundreds of millions of years of uplift, mountain building, subsidence, and stretching. The dominant cracks in these rocks, known as faults, often lay dormant for years until stresses compile, eventually overwhelming the balance to result in the sudden movement of an earthquake. This quake almost certainly occurred on one of those ancient, undisturbed faults; luckily, far away from a significant population center. Similar earthquakes have occurred in the past in Virginia, last year, and in a stronger example of a reactivated fault, the 7.0 earthquake that hit Charleston in 1883.
Essentially, because the slab of continental crust upon which our nation has built its towns, roads, and cities is being warped every second of every day, it is important that we consider the potential for even small earthquakes as we build our next generation of infrastructure. Seismicity can damage roads and buildings not just through the shaking of the structures, but also through the liquefaction of underlying sediments, through mass wasting events, and through physical displacement in fault zones. Our abilities to map the geology of the land is light-years ahead of where it once was — with satellites, GIS software, and 3-D modeling available, we can make the smart decisions that can potentially save lives and money in the future. Admittedly, not all of our nation’s fault zones can be mapped perfectly, but at the very least we can avoid the kind of concerns surrounding, for example, the nuclear power plant in Indian Point, NY. Doing our due diligence isn’t always sexy, but it’s often the best prescription for long-term success.